Neuroticism is a key component of the Five Factor Model (FFM), which categorizes personality traits into five major domains (Costa & McCrae, 1992; Goldberg, 1993). Within clinical populations, neuroticism is often identified as one of the primary factors and reflects individual variations in the inclination towards negative emotions such as sadness, anxiety, and anger. It also encompasses how individuals respond to threats, frustrations, or losses (Widiger, 2009).
The Variations in Neuroticism
Neuroticism is present in almost all models that explore higher-order traits and is sometimes referred to as Negative Affectivity (NA) or Negative Emotionality (NE) (Rothbart, Ahadi, Hershey, & Fisher, 2001; Tellegen & Waller, 2008).
While there is general agreement among major trait models regarding the higher-order domain related to negative affect, differences emerge when examining the specific facets within this domain. These differences can be attributed, at least in part, to the particular trait model being utilized. For instance, three-factor trait models (Rothbart et al., 2001; Tellegen & Waller, 2008) which do not typically include a distinct Agreeableness domain, often incorporate facets related to antagonism and aggression (which reflect disagreeableness) within the broader domain of Neuroticism (Widiger, 2009).
See also Understanding Neuroticism: Traits, Symptoms, and Causes
Within the realm of Neuroticism, there are intermediate-level divisions that distinguish subdomains related to irritable and withdrawn negative affect (De Young, Quilty, & Peterson, 2007; Shiner & Caspi, 2003). An influential model for assessing lower-order facets is the NEO Personality Inventory-Revised (NEO PI-R; Costa & McCrae, 1992). This model identifies specific facets such as Anxiety, Angry Hostility, Depression, Self-Consciousness, Vulnerability, and Impulsiveness. Similarly, the NE domain measured by the Minnesota Personality Questionnaire (MPQ) includes facets associated with alienation and stress reactivity (Tellegen & Waller, 2008). These differences in content measured at the facet level likely contribute to variations observed at the broader domain level across different assessment measures (Ormel, Bastiaansen, et al., 2013).
The Influence of Genetics on Neuroticism
Gaining insight into the factors that contribute to Neuroticism is crucial in comprehending its associations with various outcomes, including physical and mental health. Research, particularly twin studies, consistently indicates that Neuroticism, similar to other major personality traits, has a substantial heritable component. It is estimated that approximately half of the observed variation in Neuroticism can be attributed to additive genetic influences. This heritability finding aligns with broader patterns observed in psychological constructs, emphasizing the role of genetics in shaping individual differences (Turkheimer, 2000; Lahey, 2009; Widiger, 2009).
See also The Neurobiology of Neuroticism: Insights from Brain Imaging Studies
The robustness of the heritability estimate for Neuroticism has been strongly supported by a recent meta-analysis that employed item response theory methods and included a vast sample of nearly 30,000 twin pairs (van den Berg et al., 2014). Notably, research has highlighted age-related differentiation in the heritability of Neuroticism, with estimates reaching their highest point (around 50-60%) during early adolescence. Furthermore, it is interesting to observe that there are no sex differences in heritability during this developmental period (Gillespie, Evans, Wright, & Martin, 2004; Lake, Eaves, Maes, Heath, & Martin, 2000; Rettew et al., 2006; Viken, Rose, Kaprio, & Koskenvuo, 1994). However, the heritability of Neuroticism tends to decline throughout adulthood, particularly in males, leading to sex differences favoring higher heritability in females later in adulthood (Eaves, Eysenck, & Martin, 1989; Lake et al., 2000).
Despite some exceptions (e.g., van den Oord et al., 2008), previous genome-wide studies focusing on the association between common single-nucleotide polymorphisms (SNPs) and Neuroticism have generally been unsuccessful in identifying specific molecular genetic risk factors. Various studies, including meta-analyses, have reported no significant results when analyzing genome-wide association data from large samples of adults. For instance, a meta-analysis involving 17,375 adults across 10 different samples found no significant associations between Neuroticism and genetic variants (De Moor et al., 2012). Similarly, a larger study conducted by the Genetics of Personality Consortium, with over 63,000 individuals, also did not yield any significant findings for common SNPs related to Neuroticism (De Moor et al., under review).
A Candidate Gene Study for Neuroticism
The consistent failure to identify significant associations between Neuroticism and common single-nucleotide polymorphisms (SNPs) might be due to a significant portion of the genetic variation in Neuroticism being unrelated to common SNPs. Estimations of Neuroticism heritability based on similarity among individuals in common SNPs indicate a lower estimate of 15% (De Moor et al., under review) compared to approximately 50% from twin studies. This discrepancy could be attributed to twin studies capturing more than just the "main effects" of genetic variation, including gene-environment interactions not addressed in molecular genetic studies (Rijsdijk & Sham, 2002). Additionally, the 15% heritability estimate could be influenced by inadequate coverage of common SNPs or various sampling biases. However, this lower estimate suggests that less common SNPs or other genetic variants, such as repeat polymorphisms, may hold greater importance for Neuroticism. Future research should thoroughly investigate these possibilities to gain a deeper understanding of the genetic underpinnings of Neuroticism.
Candidate gene studies investigating the genetic basis of Neuroticism have primarily focused on the 5-HTTLPR repeat polymorphism within the serotonin transporter gene. This particular gene has garnered attention due to its involvement in emotion processing, given the well-established role of the serotonergic system in emotions (Leonardo & Hen, 2006). The 5-HTTLPR polymorphism is of interest because it is a functional variant that affects gene expression and is targeted by psychopharmacological treatments for internalizing disorders. Meta-analyses have indicated small yet significant differences in Neuroticism scores between individuals with at least one short 5-HTTLPR allele and those with only long alleles (Munafo, Clark, & Flint, 2005; Schinka, 2005; Schinka, Busch, & Robichaux-Keene, 2004; Sen, Burmeister, & Ghosh, 2004, 2005). Furthermore, support for the influence of 5-HTTLPR on Neuroticism comes from neuroimaging studies, which have linked the polymorphism to structural variations in the brain (Brown & Hariri, 2006; Hariri et al., 2002; Passamonti et al., 2008) that are also associated with differences in Neuroticism (Canli, 2004; Haas, Omura, Constable, & Canli, 2007; Omura, Constable, & Canli, 2005).
In addition to the 5-HTTLPR repeat polymorphism, other genetic candidates have been investigated for their association with Neuroticism. These include the 5-HTTA and 5-HT2A serotonin receptors (Golimbet et al., 2002; Lesch & Canli, 2006) as well as the G72 glutamate receptor (Rietschel et al., 2008). However, findings for these potential candidates have been mixed, with some studies showing a connection to Neuroticism and others yielding inconclusive results (Hettema, An, et al., 2006; Lang et al., 2005; Sen et al., 2003; Willis-Owen et al., 2005). Further research is needed to better understand the relationship between these genes and Neuroticism.
Environmental Influences on Neuroticism
Neuroticism is influenced not only by genetics but also by environmental factors. Studies in behavioral genetics distinguish between shared environmental influences, which affect individuals growing up in the same environment in a similar way, and nonshared environmental influences, which make individuals different from each other. While environmental factors contribute to a significant portion of the variation in Neuroticism, research suggests that this influence is primarily due to nonshared environmental factors (Fullerton, 2006; Lake et al., 2000). However, it is important to note that detecting shared environmental influences can be challenging, especially when they interact with genes (Johnson, 2007; Robinson, 2004). This means that shared environmental factors may be influenced by genes, which can increase the heritability of Neuroticism instead of reflecting unique shared environmental effects.
See also The Role of Childhood Experiences in Shaping Neuroticism
Limited research has focused on specific environmental factors that could influence Neuroticism. Studies have found associations between adult Neuroticism levels and retrospective reports of various parenting and familial factors (Allen & Lauterbach, 2007; McCrae & Costa, 1988; Reti et al., 2002; Roy, 2002; Willemsen & Boomsma, 2007). However, it is important to note that prospective studies, which consider both genetic and environmental factors, are necessary to determine potential causal effects of these factors on Neuroticism. Further investigation using well-designed prospective designs is required to gain a better understanding of the potential influences of these factors.
Stability and Change in Neuroticism
Neuroticism, like other major personality traits, tends to show stability throughout development (Caspi, 2000; Caspi et al., 2003; Caspi & Silva, 1995; Nave, Sherman, Funder, Hampson, & Goldberg, 2010). This stability is influenced by both genetic and nonshared environmental factors (De Fruyt et al., 2006) and has been observed across different samples, including community and clinical populations (De Bolle et al., 2009).
When examining stability, there are two aspects to consider: absolute stability and differential stability. Absolute stability refers to the consistency of average trait levels over time in the general population. Meta-analytic studies have indicated that mean levels of Neuroticism change during adulthood, with overall levels decreasing as individuals transition from early to later adulthood (Roberts, Walton, & Viechtbauer, 2006). This shift in adulthood may reflect greater maturation and a decrease in overall Neuroticism levels.
However, it is important to note that early developmental changes in Neuroticism might reflect a different pattern. Some researchers have suggested that the transition from childhood to adolescence involves a shift from higher to lower levels of "maturity" (Soto, John, Gosling, & Potter, 2011). To gain a better understanding of how Neuroticism levels change across different developmental periods, more research is needed.
Differential, or rank-order, stability is a key aspect examined in studies on personality development. It refers to how individuals maintain their relative ranking on a specific trait over time. Research suggests that rank-order stability is moderately present even during childhood, and it slightly increases as individuals grow older. However, the lowest levels of stability are observed for the trait of Neuroticism. These findings hold true for both young people and adults. Several studies have investigated this phenomenon, highlighting its significance (De Fruyt et al., 2006; Tackett et al., 2008; Hampson & Goldberg, 2006; Roberts & DelVecchio, 2000). When measuring any form of stability, it is crucial for researchers to consider the challenges associated with assessing trait M, especially in early life. Additionally, it is important to understand how these measurement difficulties can potentially affect estimates of stability and change.
Personality variability is another crucial aspect of personality development, particularly in relation to Neuroticism. It refers to the degree of variation in an individual's level of a trait across different situations and over time. This concept is closely related to emotional lability or reactivity, which is often considered a facet of Neuroticism, especially in models focused on personality disorders (Widiger, 2009).
A study conducted by Mroczek and Spiro (2003) discovered significant fluctuations in Neuroticism trajectories within individuals during the transition from mid to later adulthood. This finding highlights the importance of examining variations in Neuroticism within a person, in addition to studying the continuity of Neuroticism between individuals and across different circumstances.
Understanding the fluctuations in Neuroticism within individuals is crucial as it provides valuable insights into how this trait may change over time and in different contexts. By exploring both within-person variability and the consistency of Neuroticism across individuals, researchers can gain a comprehensive understanding of the dynamic nature of personality development.
Neuroticism in Childhood and Adolescence
Neuroticism, a robust higher-order personality trait, is consistently observed across various personality frameworks, including during childhood and adolescence (De Pauw in Chapter 12 and De Fruyt, De Clercq, and De Bolle in Chapter 22). However, when it comes to conceptualizing individual differences in Neuroticism/Negative Emotionality, developmental approaches have shown variations compared to adult models and among different approaches focusing on temperament and child personality (Lahey et al., 2008; Lahey, Rathouz, Applegate, Tackett, & Waldman, 2010).
It is important to consider the developmental sensitivity in understanding Neuroticism at younger ages. Different approaches, such as temperament and child personality frameworks, may provide distinct conceptualizations of Neuroticism/Negative Emotionality compared to models developed for adults. These variations in conceptualization reflect the unique considerations and perspectives in studying personality traits in children and adolescents.
Developmentally sensitive approaches to understanding Neuroticism in individuals often emphasize the role of antagonism or aggression in defining this trait (De Pauw & Mervielde, 2010; Rothbart & Bates, 2006; Tackett et al., 2012). However, there may be greater difficulty in clearly defining the more fearful or sad aspects of Neuroticism in younger individuals compared to adults.
Research on personality perception suggests that traits that are more observable tend to be perceived more accurately by informants (Tackett, 2011; Vazire, 2010). This is particularly relevant when assessing personality in early life, where reliance on informants is more common. Consequently, it is challenging to capture and define the less observable aspects of Neuroticism, such as fearfulness and sadness, during youth.
Furthermore, studies indicate that interinformant agreement is higher for externalizing psychopathology, which is characterized by antagonistic features, than for internalizing psychopathology, which is characterized by sadness and fearfulness, in young individuals (Achenbach, 2006; Achenbach et al., 1987). This finding aligns with the notion that observable behaviors associated with antagonism/aggression are more readily identified and agreed upon among informants compared to internalized emotions like sadness and fearfulness.
Key Aspects of Neuroticism in Early Personality Development
Developmental psychologists have highlighted the importance of distinguishing between the fear and irritability aspects of Neuroticism, particularly in early personality development (Rothbart & Bates, 2006; Shiner, 2010; Shiner & Caspi, 2003). However, our understanding of lower-order personality traits during early life remains limited, with sparse agreement across different frameworks (de Pauw, Mervielde, & van Leeuwen, 2009; Shiner & Caspi, 2003; Shiner & Tackett, 2014).
Notably, these mid-level traits, namely fear and irritability, are consistently represented in various models of youth personality and are analogous to the primary mid-level traits identified for Neuroticism in adult samples (De Young et al., 2007). Furthermore, it is possible to establish a connection between the extensive early literature on "difficult temperament" and the early manifestations of Neuroticism. The research on constructs related to "difficult" or "hard-to-manage" temperament often incorporates elements of negative affectivity alongside physiological features (e.g., disrupted eating and sleeping patterns) and disinhibition tendencies (e.g., Bates, Pettit, Dodge, & Ridge, 1998; Davies & Windle, 2001; Olson, Bates, Sandy, & Schilling, 2002).
Considering these findings, it becomes evident that exploring the fear and irritability aspects of Neuroticism in early life can be linked to research on difficult temperament. This association allows us to gain insights into the early manifestations of Neuroticism and its connection with negative affectivity, physiological responses, and disinhibition tendencies.
Challenges in Measuring Neuroticism
Measurement considerations play a crucial role in assessing Neuroticism, especially in young children, as existing evidence suggests that it is one of the most challenging early personality traits to measure accurately (Durbin, 2010; Tackett et al., 2008, 2012). In particular, obtaining agreement between different informants regarding Neuroticism may be more difficult compared to other aspects of early personality, especially those related to sadness and internalized negative emotions (Durbin, 2010; Tackett, 2011).
When studying Neuroticism in adults, it is commonly argued that self-report measures are particularly important and reliable for capturing individuals' experiences and perceptions (Vazire, 2010). However, this poses a significant challenge when assessing younger populations, as young children may have limited self-awareness and difficulty accurately reporting their own emotions and experiences.
To overcome these challenges, researchers need to employ innovative approaches and adapt measurement methods that are suitable for the developmental stage of young children. This may involve utilizing a combination of methods, such as observations, caregiver reports, and age-appropriate self-report measures that take into account the unique characteristics and limitations of young children.
Examining informant disagreement regarding levels of Neuroticism in youth can provide valuable insights into consequential outcomes, such as psychopathology. Research suggests that discrepancies between mothers and fathers in assessing their child's Neuroticism, even after considering the child's overall levels of Neuroticism, can incrementally predict the child's level of internalizing psychopathology (Tackett, 2011).
These findings highlight the significance of informant differences in capturing the variability of Neuroticism. Informant disagreement can serve as a powerful method for obtaining additional information about trait Neuroticism, particularly when it is more challenging to measure in younger age groups.
By considering multiple informants' perspectives, researchers gain a more comprehensive understanding of an individual's Neuroticism and its association with psychopathological outcomes. This approach allows for the identification of nuanced variations in Neuroticism that may be missed when relying solely on one informant.
Laboratory-based tasks are commonly utilized to elicit and measure temperament traits in children. However, these measures often exhibit low correlations with parent-reported Neuroticism (Durbin, 2010). Despite this, laboratory tasks offer potential advantages such as increased sensitivity to context and the ability to capture stability and change, which are crucial for a comprehensive understanding of Neuroticism (Durbin, 2010).
When measuring Neuroticism, especially in early life, it is important to employ multimethod approaches that combine various assessment methods. This includes incorporating information from multiple informants, such as parents, teachers, and caregivers, to gain a more comprehensive view of a child's Neuroticism. By utilizing different sources of information, researchers can better capture the complexities of Neuroticism and obtain a more accurate representation of a child's traits.
Furthermore, it is essential to acknowledge and explore potential discrepancies that may arise between informants and assessment methods. These discrepancies can provide valuable insights into different aspects of Neuroticism and contribute to a deeper understanding of the trait. By examining and leveraging these informant/method discrepancies, researchers can extract additional information and enrich their understanding of Neuroticism.